[Closed]My house object bouncing a little when collide with Plane floor

Ok, so todayi at last imported my first house object for my game. I take it from website that stated it is free to take, and i place it on unity.

after some time i take to correct the scale and materials, then i go to collders and rigidbody.

but when i test it, it fall through the ground (i checked "Generate Colliders" on Prefabs Inspector)

i try to do something and i at last add Box Collider.. and BUM, it is not falling through anymore, instead the house bouncing a little.. up and down in the floor.. i dont know how to show it, but if someone know how, maybe make a gif or anything i will do it to show..

what happened to my object? does this because the ground is a Plane? should i change it to a Box?

Thanks before. :)